University of Twente Student Theses
Controlling the Bistability of a Trypsin-Based Enzymatic Reaction Network
Vries, ir. P.G. de (2024) Controlling the Bistability of a Trypsin-Based Enzymatic Reaction Network.
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| Abstract: | Bistable systems are systems that can exist in one of two stable states and can dynamically switch between these states. Naturally occurring self-regulatory mechanisms such as Turing patterns, homeostasis and cell differentiation all require bistability to exist. Systems chemistry, the field that studies complex chemical networks (CRNs), has recently seen many examples of bistable chemical networks that exhibit interesting properties. Many agree that synthesizing controllable bistable chemical networks will ultimately aid in the creation of artificial life-like systems. For a system to show bistability, it must contain a feedback loop, which is a mechanism where part of the system’s output is redirected back into the input. The strength of the feedback directly determines the system’s bistable conditions. The most straightforward chemical analogue of feedback is autocatalysis, a type of reaction in which the product of a conversion reaction catalyzes its own formation. In such a case, the strength of the feedback is the rate of autocatalysis. By chemically changing the rate of autocatalysis, the bistability of a network can be controlled. Bistability in CRNs has been widely studied, but experimental demonstrations of control over bistability by tuning the strength of the chemical feedback is rare. In this work, we use a well-known enzymatic autocatalytic chemical network which has been shown to be bistable. Trypsin (Tr) is the central molecule, which is formed autocatalytically by cleavage of its precursor, trypsinogen (Tg). To enable us to control the release of Tr and to switch between steady states, soybean trypsin inhibitor (STI) is added. This network is bistable because it shows two possible states, a high [Tr] state and a low [Tr] state, when placed in the right conditions. Recent work in our group has shown that, by using lanthanide ions such as La3+ and Nd3+, the rate of autocatalysis can be controlled. In this work, we introduced La3+, which undergoes the simplest mechanism out of these ions, to the trypsin autocatalytic network. We aimed to address the missing link between chemical feedback and bistability in current systems chemistry by introducing La3+ as a control parameter to shift the network’s bistability. We performed an experimental investigation of the effect of La3+ on the autocatalysis in the presence and absence of constant flow, and on the bistability of the network. We found that La3+ increases the rate of autocatalysis until a saturation point around 1.0 mM in batch. From the batch data, we chose experimental conditions to work in flow, where we found that using La3+ indeed shifts the bistability. Higher concentrations of La3+ caused a need for higher inhibitor concentrations to suppress the high- [Tr] steady state and increased the magnitude of this high-[Tr] state. We envision that the results reported here will inspire more work into the control of various other bistable networks with interesting functionalities by tuning the feedback loops. |
| Item Type: | Essay (Master) |
| Faculty: | TNW: Science and Technology |
| Subject: | 35 chemistry, 51 materials science |
| Programme: | Chemical Engineering MSc (60437) |
| Link to this item: | https://purl.utwente.nl/essays/104875 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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